An increasing series of studies show that hearing loss increases the risk of dementia. The greater the hearing loss, the greater the risk.

Theories abound as to why – including some included in a recent article by Pam Belluck of the New York Times: People with hearing loss become socially isolated. An underlying process affects both hearing loss and dementia. Cognitive underload increases – it’s hard to process the words when you can’t understand them.

Which may actually partially get at what is really going on.

The body is an information processor. Enormous data comes to be sifted, recognized, utilized, summarized, eventually dumped. A large, executive part of this information processing goes on in the brain.

When a person loses hearing, they lose an enormous information load to the brain. And most of this is not conscious – as is most of the information any human being normally experiences.

Turning Off the Ears

You can’t turn off your ears. You can close the eyes, refuse to taste a new food, stopper your nose. Yet hearing cannot be stopped.

Unless you became deaf.

Then enormous levels of environmental signals become lost and not replaced. Signals you need to place yourself in three dimensional space. Signals that determine where you are – and who you are with. Signals that place you among friends or foes. Signals that tell you there is danger or that you are safe.

And many of this vast host of signals never reach consciousness – sounds we hear but do not recognize, recall, or linguistically remember.

Because most of what comes into the brain is not material we can put into explicit verbal form. Yet because dementia is a cognitive disease, we think only cognitive inputs matter.

Nonsense.

A critical factor in most dementias is atherosclerosis. Increase it through high blood pressure, stress, diabetes or what have you and dementia rates go up dramatically.

The converse is also true.

The Okinawan study looked at many centenarians. When they died their brains were biopsied. Many showed neuropathology of advanced Alzheimer’s disease.

Except they did not show dementia clinically.The brains looked awful – the behavior was not. Their memory worked.

Why? The arteries of those without memory loss were clean – without clogging, huge plaques, sharp narrowing and kinks.

For most biological events remain unappreciated. High blood pressure is generally not a cognitive problem. Unless checked, people don’t know they have it.

And what people don’t consciously experience still dramatically affects their health.

Cognitive Vs. Non-Cognitive Information

What is the difference in brain oxygen flow between a “resting”, sleeping person and one in high level exercise?

Less than 1%.

The brain is always “on.” Always taking in and processing information. Always learning.

It’s hard to know determine how much of this is not conscious. But estimates are that in “default mode”, where the brain is calm and at rest, about 90-95% of brain activity cannot be accounted for.

Translation – most of what we do lies under the hood. And we don’t know what it is.

Is it “housekeeping”? Are these “housekeeping” functions “minor” details like controlling the immune system or figuring out how to modulate cardiac blood flow? Changing the mix of nutrients coming out of the liver and going to the muscles?

The truth is probably this – most of what goes on in the brain is no less open to us that what happens with “dark energy” and “dark matter”. Both together are reckoned to together constitute 96% of the universe.

Which means that physics has been talking, studying, and witnessing 4% of the universe for the last several centuries.

That’s probably a higher percentage than overall level of brain actions we presently investigate and “understand.” And despite what George Orwell wrote, ignorance is not strength.

Walking and Reading

Which involves more information to the brain – walking across the street or reading a difficult mathematics text?

Most would immediately point to the math text. Partial differential equations are difficult for most people. Hard labor, lots of information.

Walking across the street involves being bombarded by hundreds of different bacteria, viruses, prions, fungi. Thousands of different chemicals assault our nasal passages, throats, skin. The immune system must respond to all.

And we must respond, adjust and adapt to our movement through space, the shifting effects of light, the powerful smells and noise of life. Not to mention fending off fast moving cabs and trucks.

So we should not be surprised that walking even 20 minutes a day increases brain cell growth. The information load coming into the brain and body is gigantic. So big we have to grow new memory stores for it.

And what happens is not conscious.

Preventing Alzheimer’s

People who wish to avoid dementia are given the usual laundry list of things to do – eat “right”, exercise, keep your blood pressure controlled.

They are not told that increasing the information load to the brain – on a daily basis – may be what really helps.

Yet the evidence is there:

Older folk who get out of the house more – just travelling out – have far less dementia. Novelty – new information – is good for the brain.

People with higher academic study years and learning hold off Alzheimer’s longer – though when it hits it may strike more quickly.

Those with strong social ties and engagement experience less dementia. Think of the information issues involved in interacting with other humans and you’ll immediately recognize even a short conversation takes a great deal of data to process and understand.

Exercise – including not such stirring stuff as walking – keeps Alzheimer’s at bay.

People who lack large information inputs – as occurs in hearing loss – get dementia earlier.

And at last week’s AAAS conference in Boston, data showing that dementia may spread “informationally” – to previously unaffected areas which become metabolically correlated with diseased regions.

Regeneration is the key. Lots of information coming into body and brain leads to lots of processing, lots of new brain cell connections, new brain cell growth.

In coming decades we’ll get a better idea of just what the healthiest forms of information are – and when they become too much. Drug overdoses, as in cocaine, may activate the brain and at the same time kill it.

But broadly useful forms of information are known – social engagement; physical movement; foods that fit what humans have evolved to eat.

They’re the same things that keep people healthy in so many ways – heart healthy, brain healthy, lung healthy.